Short-circuiting device for electric motors



H. L. JOHNSTON ET A1.

SHORT CIRCUITING DEVICE FOR ELECTRIC MOTORS Filed March 25. 1925 2 Sheets-Sheet 1 Fig-l l@ 3 .g4 y @5 g3 4 ATTORNEYS.

H. L. JOHNSTON ET A1.

SHORT CIRGUITING DEVICE EOE ELECTRIC Mo'roRs Filed March 25. 1925 sheets-sheer 2 MMO ATTORNEYS.

Patented Apr. 10, '1928.

UNITED STATES PATENT OFFICE.

HERBERT L. JOHNSTON AND MILTON4 K. AKRS, OF TROY, OHIO,A ASSIGNORS TO THE HOBART MANUFACTURING COMPANY, OF TROY, OHIO, A CORPORATION F OHIO.

SHOBT-CIRCUITING DEVICE FOR ELECTRIC MOTORS.

Application led March 23,' 1925. Serial No. 17,522.

Our inventionrelatesto devices for use in connection with alternating current motors when it is desired to change the operation of such motors from repulsion to in- 6 duction when a predetermined speed has been reached.

This change is accomplished by short circuiting the commutator of a wound rotor.

Among the objects of our invention is .the

10 provision of simple means for accompllshing such a short circuiting, whereby a sindle spring, whose action is readily adjustable and which acts as a compression spring, op- 'poses the action of the short circuiting disk. The parts are held together without screws and can be quickly assembled and installed. The short circuiting element is in the form of disk having a resilient edge, which will contact evenly and the take-up for the action of the spring and the disk is accomplished by presslng in o'n certain parts against the spring and turning them through part of a revolution.

These objects and other advantages to be noted, we accomplish by that certain construction and arrangement of parts to be lhereinafter more specifically pointed out and claimed.

'In the drawings: l

Figure 1 is a central' vertical elevation, partly broken away, taken through the device, showing relative position of parts when the motor is stopped or operating as a repulsion motor. x

Figure 2 is a central vertical section taken through the device, showin the parts in the positions they take when t e motor is up to speed and operating as an induction motor.

Figure 3"is a the weight bars.

Fi ure 4 is a perspective view of the short circulting disk.

Fi ure 5 is a perspective view of the adjusta le hub.

We have not shown the parts of a motor aside from the armature shaft and the commutator bar holder casting thereon. It will be understood that any usual form of alternating current motor and brush device ma be employed.

n the shaft 1 of the armature is mountperspective view of one of ed the commutator casting 2, in which are the commutator bars-3 insulated from the casting at 4. v

A plate 5 is provided having a hub 6, which fits slidably over thearinature shaft andis held inwardly toward the commutator by means of a pin 7 set into the shaft at a proper point. The commutator castlng is shown as formed with a depression 2, which acts as a housing for parts of the device. It will be understood that this exact method of housing the parts need not be followed except for the saving of space pluri saving of size in the short circuiting 'lhe hub 6 has a series of notches 8 cut therein, the notches opposite each other having the same depth, but each opposed pair varying in depth. This permits of adjusting the position of the hub along the shaft.

Over the armature shaft, inside of the hub 6, is set a sleeve 9, which carries in a groove therein, the short circuiting disk 10. This disk is cup-shaped so as to bring its edges into proper position with relation to the ends of the commutator bars, which are exposed at the outer face o f the commutator casting. f

The disk is formed at its edges with a series of slots 11, which separate the edges into a series of interspaced tongues which have considerable resiliency. The body of the disk has a series of rectangular slots cut therein, as at 12, in which are to be set the centrifugally controlled elements.

These centrifugally controlled elements are formed as heavy pieces having bars 13, which lie normally in line with the armature shaft. They have necks 12a which lie in the slots in the disk l0. We have also shown an additional disk or washer 15, which is mounted with the disklO, and is used for purposes of stiffness.

The Weights have also angle ends 14, which lie normally fiat against the plate 5,

same beingfpart of the hub 6.

` sprin 16 under tension, which can he varied y changing the. notches of the hub `ily out centrifugally,

which engage the pin.

In operation the motor ywill start as a repulsion motor and as it gains speed the weights or centrifugal so as to tip on the plate 5, the outer corners of the portion 14 acting as the fulcrum. The weights will also tend'to rock within the slots of the short circuiting disk and washer.

This action will force the disk away from mutator bar ends until the resilient edge of the disk contacts with the bars and short short circuiting l circuits th^ armature coils.-

l when it is started up. i

is readily adjusted as noted. The resilient tongued edge ofthe disk acts effectively to short circuit all bars and the disk is lso mounted on the sleeve 9 that it must move axially to the armature shaft so as to ,make a uniform contact. i

The weights will return to normal vposition as soon as the motor slows downto a stop,.ready to begin the cycle over again 3As stated above, we do not wish 'to be construed as limiting our invention to one set of mechanism, because of our failure to describe such' alternative structures, .as ap.

pear tous readilyusable instead of those described.

Having `thus described our invention, what we claim as new and desire to secure by Letters Patent, is f Y 1. In combination with an amature shaft,

short circuiting position,

members will tend. to

the plate 5 towardthe com'- l a commutator. having bars, a sleeve on the shaft, a short circuiting disk on the sleeve, spring means to hold the disk away from centrifugal means and a relatively fixed member on the shaft, between which and the short circuiting device thc centrifugal means acts, said member being`adjustable along the shaft, said adjustment comprising a pin in the'shaft and a hub havinga series of opposed notches to engage the pin, said notches having varying depth.

2. In combination with an armature shaft, a commutator having bars, a sleeve on the shaft, a short circuiting disk on the sleeve, spring means to hold the disk away from short circuitingposition, and a relatively fixed member on the shaft, between which and the short circuiting device the centrifugal means acts, said member being adjustable along the4 shaft, saidadjustment' comprising a pin in the shaft and a hub having a series of'opposed notches to engage the pin, said notches having varyingv depth, and said disk having a resilient edge for contact vwith the ends of the commutator bars.

3. In combination with an armature shaft,

a commutator having bars, a-sleeve on the shaft, a short circuiting disk on the sleeve, a coil spring concentrically mounted on said shaft for holding said disc away from short circuiting position, centrifugal means for lvmoving said disc to short circuitiig position, an adjustably mounted member on said `shaft between which -and the short circuiting device said centrifugal means acts, and the adjustability of said member for varying the tension of said spring being provided I' by pin and s lot connections.

HERBERT' L. JOHNSTON.

MILTON K.' AKERS..

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